This invention relates to a signal recording and reproducing system of the type, in which a recording/reproducing head is moved stepwise in the direction of width of a single recording tape for tracing successive recording tracks arranged in the direction of the tape width in recording or playback, and, more particularly, to a device for detecting the edge of the signal recording tape, that is, for detecting the fact that the head is brought to either edge of the tape, to thereby control the movement of the head.
In the afore-mentioned recording and reproducing system, for instance a video tape recorder of a stationary head type, the head is fed stepwise in the direction of the width of an endless tape by a predetermined small pitch corresponding to the recording track pitch of the tape every time the endless tape completes one excursion. In this type of video tape recorder, when the head is brought to either edge of the endless tape, i.e., brought to a position corresponding to the end track in the tape, it is necessary to stop the endless tape or return the head in the reverse direction by detecting this. To this end, it has been proposed to provide a microswitch at a position corresponding to the edge of the tape such that an actuator of this microswitch can be actuated by the head. With this microswitch, however, the position of the actuator when the switch is turned on is different from the position when the switch is turned off, that is, the microswitch has a peculiar hysteresis involved in its on-off operation. Therefore, for ensuring reliable on-off operation of the microswitch it is necessary to give a displacement stroke greater than the afore-mentioned hysteresis to the actuator of the microswitch. This means that an extra distance has to be provided for the movement of the head between adjacent recording tracks, that is, the track pitch has to be increased, in order to provide for the afore-mentioned displacement stroke of the microswitch actuator. To increase the track pitch, however, is very undesirable for the video tape recorder, which is small in size and has to meet the demand for recording and reproduction of high quality images.